Miter saw with improved safety system

ABSTRACT

A miter saw is disclosed having a base, a blade supported by the base, a detection system adapted to detect a dangerous condition between a person and the blade, and a reaction system associated with the detection system to cause a predetermined action to take place upon detection of the dangerous condition. The blade is rotatable, and moves into a cutting zone to cut a workpiece. The predetermined action may be to stop the blade from rotating, to create an impulse against movement of the blade into the cutting zone, or to cause the blade to move away from the cutting zone.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of the following U.S. PatentApplications, all of which are hereby incorporated by reference in theirentireties for all purposes:

Ser. No. 09/929,426, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,200, filed Aug. 14, 2000;

Ser. No. 09/929,221, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,211, filed Aug. 14, 2000;

Ser. No. 09/929,240, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,056, filed Aug. 14, 2000;

Ser. No. 09/929,227, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,170, filed Aug. 14, 2000;

Ser. No. 11/401,050, filed Apr. 10, 2006, which is a continuation of anumber of applications including Ser. No. 09/929,241, filed Aug. 13,2001, issuing as U.S. Pat. No. 7,024,975 on Apr. 11, 2006, which in turnclaimed the benefit of and priority from a number of U.S. ProvisionalPatent Applications including Ser. No. 60/225,169, filed Aug. 14, 2000;

Ser. No. 09/929,242, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,089, filed Aug. 14, 2000;

Ser. No. 10/984,643, filed Nov. 8, 2004, which is a continuation of anumber of applications, including Ser. No. 10/205,164, filed Jul. 25,2002, issuing as U.S. Pat. No. 6,945,149 on Sep. 20, 2005, which in turnclaimed the benefit of and priority from U.S. Provisional PatentApplication Ser. No. 60/307,756, filed Jul. 25, 2001, and Ser. No.10/202,928, filed Jul. 25, 2002, issuing as U.S. Pat. No. 7,000,514 onFeb. 21, 2006, which in turn claimed the benefit of and priority fromU.S. Provisional Patent Application Ser. No. 60/308,492, filed Jul. 27,2001;

Ser. No. 09/929,236, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,201, filed Aug. 14, 2000;

Ser. No. 11/061,162, filed Feb. 18, 2005, which is a continuation ofSer. No. 09/929,244, filed Aug. 13, 2001, issuing as U.S. Pat. No.6,857,345 on Feb. 22, 2005, which in turn claimed the benefit of andpriority from a number of U.S. Provisional Patent Applications includingSer. No. 60/225,212, filed Aug. 14, 2000;

Ser. No. 09/929,237, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,059, filed Aug. 14, 2000;

Ser. No. 09/929,234, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,094, filed Aug. 14, 2000;

Ser. No. 09/929,425, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,210, filed Aug. 14, 2000;

Ser. No. 11/190,111, filed Jul. 25, 2005, which is a continuation of anumber of applications including Ser. No. 09/929,226, filed Aug. 13,2001, issuing as U.S. Pat. No. 6,920,814 on Jul. 26, 2005, which in turnclaimed the benefit of and priority from a number of U.S. ProvisionalPatent Applications including Ser. No. 60/225,206, filed Aug. 14, 2000;Ser. No. 10/205,164, filed Jul. 25, 2002, issuing as U.S. Pat. No.6,945,149 on Sep. 20, 2005, which in turn claimed the benefit of andpriority from U.S. Provisional Patent Application Ser. No. 60/307,756,filed Jul. 25, 2001; and Ser. No. 10/202,928, filed Jul. 25, 2002,issuing as U.S. Pat. No. 7,000,514 on Feb. 21, 2006, which in turnclaimed the benefit of and priority from U.S. Provisional PatentApplication Ser. No. 60/308,492, filed Jul. 27, 2001;

Ser. No. 09/929,235, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,058, filed Aug. 14, 2000;

Ser. No. 09/929,238, filed Aug. 13, 2001, which claims the benefit ofand priority from a number of U.S. Provisional Patent Applicationsincluding Ser. No. 60/225,057, filed Aug. 14, 2000;

Ser. No. 09/676,190, filed Sep. 29, 2000, which claims the benefit ofand priority from the following U.S. Provisional Patent Applications:Ser. No. 60/182,866, filed Feb. 16, 2000, and Ser. No. 60/157,340, filedOct. 1, 1999;

Ser. No. 10/053,390, filed Jan. 16, 2002, which is acontinuation-in-part of a number of applications including Ser. No.09/676,190, filed Sep. 29, 2000; and Ser. No. 10/053,390 also claims thebenefit of and priority from U.S. Provisional Patent Application Ser.No. 60/270,011, filed Feb. 20, 2001;

Ser. No. 11/348,580, filed Feb. 6, 2006, which is a continuation of anumber of applications including Ser. No. 10/052,705, filed Jan. 16,2002, issuing as U.S. Pat. No. 6,994,004 on Feb. 7, 2006, which in turnclaimed the benefit of and priority from the following U.S. ProvisionalPatent Applications: Ser. No. 60/270,011, filed Feb. 20, 2001, Ser. No.60/270,941, filed Feb. 22, 2001, Ser. No. 60/270,942, filed Feb. 22,2001, Ser. No. 60/273,177, filed Mar. 2, 2001, and Ser. No. 60/273,178,filed Mar. 2, 2001; and Ser. No. 11/348,580 also claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/667,485, filed Mar. 31, 2005;

Ser. No. 10/932,339, filed Sep. 1, 2004, which is a continuation of Ser.No. 10/047,066, filed Jan. 14, 2002, issuing as U.S. Pat. No. 6,945,148on Sep. 20, 2005, which in turn claimed the benefit of and priority fromthe following U.S. Provisional Patent Applications: Ser. No. 60/270,011,filed Feb. 20, 2001, Ser. No. 60/270,941, filed Feb. 22, 2001, Ser. No.60/270,942, filed Feb. 22, 2001, Ser. No. 60/273,177, filed Mar. 2,2001, Ser. No. 60/273,178, filed Mar. 2, 2001, and Ser. No. 60/273,902,filed Mar. 6, 2001; and Ser. No. 10/392,339 is also a continuation ofSer. No. 10/050,085, filed Jan. 14, 2002;

Ser. No. 10/100,211, filed Mar. 13, 2002, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/275,583, filed Mar. 13, 2001;

Ser. No. 11/256,757, filed Oct. 24, 2005, which is a continuation ofSer. No. 09/955,418, filed Sep. 17, 2001, issuing as U.S. Pat. No.6,957,601 on Oct. 25, 2005, which in turn claimed the benefit of andpriority to a number of U.S. Provisional Patent Applications, including:Ser. No. 60/233,459, filed Sep. 18, 2000, Ser. No. 60/270,011, filedFeb. 20, 2001, Ser. No. 60/270,941, filed Feb. 22, 2001, Ser. No.60/270,942, filed Feb. 22, 2001, Ser. No. 60/273,177, filed Mar. 2,2001, Ser. No. 60/273,178, filed Mar. 2, 2001, Ser. No. 60/273,902,filed Mar. 6, 2001, Ser. No. 60/275,594, filed Mar. 13, 2001, Ser. No.60/275,595, filed Mar. 13, 2001, Ser. No. 60/279,313, filed Mar. 27,2001, Ser. No. 60/292,081, filed May 17, 2001, Ser. No. 60/292,100,filed May 17, 2001, Ser. No. 60/298,207, filed Jun. 13, 2001, Ser. No.60/302,937, filed Jul. 2, 2001, Ser. No. 60/302,916, filed Jul. 3, 2001,Ser. No. 60/306,202, filed Jul. 18, 2001, Ser. No. 60/307,657, filedJul. 25, 2001, Ser. No. 60/308,492, filed Jul. 27, 2001, and Ser. No.60/312,141, filed Aug. 13, 2001;

Ser. No. 10/146,527, filed May 15, 2002, which claims the benefit of andpriority from U.S. Provisional Patent Application Ser. No. 60/292,100,filed May 17, 2001;

Ser. No. 11/218,356, filed Sep. 2, 2005, which is a continuation of anumber of applications including Ser. No. 10/146,527, filed May 15,2002, which in turn claims the benefit of and priority from U.S.Provisional Patent Application Ser. No. 60/292,100, filed May 17, 2001;

Ser. No. 10/172,553, filed Jun. 13, 2002, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/298,207, filed Jun. 13, 2001;

Ser. No. 10/189,031, filed Jul. 2, 2002, which claims the benefit of andpriority from U.S. Provisional Patent Application Ser. No. 60/302,937,filed Jul. 2, 2001;

Ser. No. 10/189,027, filed Jul. 2, 2002, which claims the benefit of andpriority from U.S. Provisional Patent Application Ser. No. 60/302,916,filed Jul. 3, 2001;

Ser. No. 11/353,423, filed Feb. 13, 2006, which is a continuation ofSer. No. 10/785,361, filed Feb. 23, 2004, issuing as U.S. Pat. No.6,997,090 on Feb. 14, 2006, which in turn is a continuation of Ser. No.10/215,929, filed Aug. 9, 2002, which in turn claimed the benefit of andpriority to U.S. Provisional Patent Application Ser. No. 60/312,141,filed Aug. 13, 2001;

Ser. No. 11/208,214, filed Aug. 19, 2005, which is a continuation ofSer. No. 10/251,576, filed Sep. 20, 2002, which in turn was acontinuation-in-part of Ser. No. 10/197,975, filed Jul. 18, 2002, andwhich claimed the benefit of and priority to U.S. Provisional PatentApplication Ser. No. 60/323,975, filed Sep. 21, 2001, and Ser. No.11/208,214 is also a continuation-in-part of Ser. No. 09/676,190, filedSep. 29, 2000, which in turn claimed the benefit of and priority fromU.S. Provisional Patent Application Ser. No. 60/157,340, filed Oct. 1,1999 and Ser. No. 60/182,866, filed Feb. 16, 2000;

Ser. No. 10/243,042, filed Sep. 13, 2002, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/324,729, filed Sep. 24, 2001;

Ser. No. 10/292,607, filed Nov. 12, 2002, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/335,970, filed Nov. 13, 2001;

Ser. No. 10/345,630, filed Jan. 15, 2003, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/349,989, filed Jan. 16, 2002;

Ser. No. 10/341,260, filed Jan. 13, 2003, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/351,797, filed Jan. 25, 2002;

Ser. No. 10/643,296, filed Aug. 18, 2003, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/406,138, filed Aug. 27, 2002;

Ser. No. 10/794,161, filed Mar. 4, 2004, which claims the benefit of andpriority from U.S. Provisional Patent Application Ser. No. 60/452,159,filed Mar. 5, 2003;

Ser. No. 10/923,290, filed Aug. 20, 2004, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/496,550, filed Aug. 20, 2003;

Ser. No. 10/923,273, filed Aug. 20, 2004, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/496,574, filed Aug. 20, 2003;

Ser. No. 11/401,774, filed Apr. 11, 2006, which is a continuation of anumber of applications including Ser. No. 11/027,322, filed Dec. 31,2004, which in turn claimed the benefit of and priority from U.S.Provisional Patent Application Ser. No. 60/533,598, filed Dec. 31, 2003,and Ser. No. 11/401,774 is also a continuation of Ser. No. 09/676,190,filed Sep. 29, 2000, which in turn claimed the benefit of and priorityfrom U.S. Provisional Patent Application Ser. No. 60/157,340, filed Oct.1, 1999 and Ser. No. 60/182,866, filed Feb. 16, 2000;

Ser. No. 10/923,282, filed Aug. 20, 2004, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/496,568, filed Aug. 20, 2003;

Ser. No. 11/027,600, filed Dec. 31, 2004, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/533,791, filed Dec. 31, 2003;

Ser. No. 11/107,499, filed Apr. 15, 2005;

Ser. No. 11/027,254, filed Dec. 31, 2004, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/533,852, filed Dec. 31, 2003;

Ser. No. 11/026,114, filed Dec. 31, 2004, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/533,811, filed Dec. 31, 2003;

Ser. No. 11/026,006, filed Dec. 31, 2004, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/533,575, filed Dec. 31, 2003;

Ser. No. 11/045,972, filed Jan. 28, 2005, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/540,377, filed Jan. 29, 2004;

Ser. No. 11/395,502, filed Mar. 31, 2006, which claims the benefit ofand priority from U.S. Provisional Patent Application Ser. No.60/667,485, filed Mar. 31, 2005; and

Ser. No. 11/098,984, filed Apr. 4, 2005, which is a continuation of aSer. No. 09/929,238, filed Aug. 13, 2001, Ser. No. 10/047,066, filedJan. 14, 2002, Ser. No. 10/051,782, filed Jan. 15, 2002, issuing as U.S.Pat. No. 6,877,410 on Apr. 12, 2005, which in turn claimed the benefitof and priority from the following U.S. Provisional Patent Applications:Ser. No. 60/270,011, filed Feb. 20, 2001, Ser. No. 60/270,941, filedFeb. 22, 2001, Ser. No. 60/270,942, filed Feb. 22, 2001, Ser. No.60/273,177, filed Mar. 2, 2001, Ser. No. 60/273,178, filed Mar. 2, 2001,Ser. No. 60/273,902, filed Mar. 6, 2001, and Ser. No. 60/275,594, filedMar. 13, 2001; and Ser. No. 11/098,984 is also a continuation of Ser.No. 10/052,806, filed Jan. 16, 2002, issuing as U.S. Pat. No. 6,880,440on Apr. 19, 2005, which in turn claimed the benefit of and priority fromthe following U.S. Provisional Patent Applications: Ser. No. 60/270,011,filed Feb. 20, 2001, Ser. No. 60/270,941, filed Feb. 22, 2001, and Ser.No. 60/270,942, filed Feb. 22, 2001; and Ser. No. 11/098,984 is also acontinuation of Ser. No. 10/643,296, filed Aug. 18, 2003, and Ser. No.10/932,339, filed Sep. 1, 2004.

FIELD

The present invention relates to miter saws, and more particularly to amiter saw with a high-speed safety system.

BACKGROUND

Miter saws are a type of woodworking machinery used to cut workpieces ofwood, plastic and other materials. Miter saws typically include a baseupon which workpieces are placed and include a circular saw blademounted on a pivot arm. A person uses a miter saw by placing a workpieceon the base beneath the upraised blade and then bringing the blade downvia the pivot arm to cut the workpiece. Miter saws present a risk ofinjury to users because the spinning blade is often exposed when in use.Furthermore, users often use their hands to position and supportworkpieces beneath the blade, which increases the chance that an injurywill occur.

The present invention provides miter saws with improved safety systemsthat are adapted to detect the occurrence of one or more dangerous, ortriggering, conditions during use, such as when a user's body contacts aspinning saw blade. When such a condition occurs, a safety system isactuated to limit or even prevent injury to the user.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a miter saw with a fast-actingsafety system according to the present invention.

FIG. 2 is a schematic diagram of an exemplary safety system configuredto stop the miter saw blade.

FIG. 3 is a schematic side elevation of an exemplary miter saw having asafety system configured to stop both the rotation and downward movementof the blade.

FIG. 4 is similar to FIG. 3 but shows the pivot arm assembly pivoteddownward into the cutting zone.

FIG. 5 is a partial top plan view of the miter saw of FIG. 3, with aportion of the housing cut away to show the brake pawl.

FIG. 6 is a schematic side elevation of another exemplary miter sawhaving an alternative safety system configured to stop both the rotationand downward movement of the blade.

FIG. 7 is similar to FIG. 6 but shows the pivot arm assembly pivotedupward away from the cutting zone.

FIG. 8 is a partial top plan view of the miter saw of FIG. 6, with aportion of the housing cut away to show the brake mechanism.

FIG. 9 is similar to FIG. 6 but shows the radial support arms uncoupledfrom the brace member to pivot the cartridge below the housing forreplacement.

DETAILED DESCRIPTION

A miter saw according to the present invention is shown schematically inFIG. 1 and indicated generally at 10. Miter saw 10 may be any of avariety of different types and configurations of miter saw adapted forcutting workpieces, such as wood, plastic, etc. Miter saw 10 includes anoperative structure 12 having a cutting tool 14 and a motor assembly 16adapted to drive the cutting tool. Miter saw 10 also includes a safetysystem 18 configured to minimize the potential of a serious injury to aperson using miter saw 10. Safety system 18 is adapted to detect theoccurrence of one or more dangerous, or triggering, conditions duringuse of miter saw 10. If such a dangerous condition is detected, safetysystem 18 is adapted to engage operative structure 12 to limit anyinjury to the user caused by the dangerous condition.

Miter saw 10 also includes a suitable power source 20 to provide powerto operative structure 12 and safety system 18. Power source 20 may bean external power source such as line current, or an internal powersource such as a battery. Alternatively, power source 20 may include acombination of both external and internal power sources. Furthermore,power source 20 may include two or more separate power sources, eachadapted to power different portions of miter saw 10.

It will be appreciated that operative structure 12 may take any one ofmany different forms, depending on the type of miter saw 10. As will bedescribed in more detail below, operative structure 12 typically takesthe form of an arm pivotally coupled to a base. Cutting tool 14 ismounted on the arm and pivotal toward a workpiece supported by the base.Alternatively, the arm may be both pivotally and slidably coupled to thebase.

Motor assembly 16 includes one or more motors adapted to drive cuttingtool 14. The motors may be either directly or indirectly coupled to thecutting tool. Typically, motor assembly 16 is mounted on the pivot armand directly coupled to the cutting tool.

Safety system 18 includes a detection subsystem 22, a reaction subsystem24 and a control subsystem 26. Control subsystem 26 may be adapted toreceive inputs from a variety of sources including detection subsystem22, reaction subsystem 24, operative structure 12 and motor assembly 16.The control subsystem may also include one or more sensors adapted tomonitor selected parameters of miter saw 10. In addition, controlsubsystem 26 typically includes one or more instruments operable by auser to control the miter saw. The control subsystem is configured tocontrol miter saw 10 in response to the inputs it receives.

Detection subsystem 22 is configured to detect one or more dangerous, ortriggering, conditions during use of miter saw 10. For example, thedetection subsystem may be configured to detect that a portion of theuser's body is dangerously close to, or in contact with, a portion ofcutting tool 14. As another example, the detection subsystem may beconfigured to detect the rapid movement of a workpiece due to kickbackby the cutting tool, as is described in U.S. Provisional PatentApplication Ser. No. 60/182,866, filed Feb. 16, 2000 and U.S. patentapplication Ser. No. 09/676,190, filed Sep. 29, 2000, the disclosures ofwhich are herein incorporated by reference. In some embodiments,detection subsystem 22 may inform control subsystem 26 of the dangerouscondition, which then activates reaction subsystem 24. In otherembodiments, the detection subsystem may be adapted to activate thereaction subsystem directly.

Once activated in response to a dangerous condition, reaction subsystem24 is configured to engage operative structure 12 quickly to preventserious injury to the user. It will be appreciated that the particularaction to be taken by reaction subsystem 24 will vary depending on thetype of miter saw 10 and/or the dangerous condition that is detected.For example, reaction subsystem 24 may be configured to do one or moreof the following: stop the movement of cutting tool 14, disconnect motorassembly 16 from power source 20, place a barrier between the cuttingtool and the user, retract the cutting tool from its operating position,etc. The reaction subsystem may be configured to take a combination ofsteps to protect the user from serious injury. Placement of a barrierbetween the cutting tool and teeth is described in more detail in U.S.Provisional Patent Application Ser. No. 60/225,206, filed Aug. 14, 2000and U.S. patent application Ser. No. 09/929,226, filed Aug. 13, 2001,the disclosures of which are herein incorporated by reference.Retraction of the cutting tool from its operating position is describedin more detail in U.S. Provisional Patent Application Ser. No.60/225,089, filed Aug. 14, 2000 and U.S. patent application Ser. No.09/929,242, filed Aug. 13, 2001, the disclosures of which are hereinincorporated by reference.

The configuration of reaction subsystem 24 typically will vary dependingon which action(s) are taken. In the exemplary embodiment depicted inFIG. 1, reaction subsystem 24 is configured to stop the movement ofcutting tool 14 and includes a brake mechanism 28, a biasing mechanism30, a restraining mechanism 32, and a release mechanism 34. Brakemechanism 28 is adapted to engage operative structure 12 under theurging of biasing mechanism 30. During normal operation of miter saw 10,restraining mechanism 32 holds the brake mechanism out of engagementwith the operative structure. However, upon receipt of an activationsignal by reaction subsystem 24, the brake mechanism is released fromthe restraining mechanism by release mechanism 34, whereupon, the brakemechanism quickly engages at least a portion of the operative structureto bring the cutting tool to a stop.

It will be appreciated by those of skill in the art that the exemplaryembodiment depicted in FIG. 1 and described above may be implemented ina variety of ways depending on the type and configuration of operativestructure 12. Turning attention to FIG. 2, one example of the manypossible implementations of miter saw 10 includes a cutting tool 14 inthe form of a circular blade 40 mounted on a rotating shaft or arbor 42.Blade 40 includes a plurality of cutting teeth (not shown) disposedaround the outer edge of the blade. As described in more detail below,brake mechanism 28 is adapted to engage the teeth of blade 40 and stoprotation of the blade.

In the exemplary implementation, detection subsystem 22 is adapted todetect the dangerous condition of the user coming into contact withblade 40. The detection subsystem includes a sensor assembly, such ascontact detection plates 44 and 46, capacitively coupled to blade 40 todetect any contact between the user's body and the blade. Typically, theblade, or some larger portion of cutting tool 14 is electricallyisolated from the remainder of miter saw 10. Alternatively, detectionsubsystem 22 may include a different sensor assembly configured todetect contact in other ways, such as optically, resistively, etc. Inany event, the detection subsystem is adapted to transmit a signal tocontrol subsystem 26 when contact between the user and the blade isdetected. Various exemplary embodiments and implementations of detectionsubsystem 22 are described in more detail in U.S. Provisional PatentApplication Ser. No. 60/225,200, filed Aug. 14, 2000, U.S. patentapplication Ser. No. 09/929,426, filed Aug. 13, 2001, U.S. ProvisionalPatent Application Ser. No. 60/225,211, filed Aug. 14, 2000, U.S. patentapplication Ser. No. 09/929,221, filed Aug. 13, 2001, U.S. ProvisionalPatent Application Ser. No. 60/270,011, filed Feb. 20, 2001, and U.S.patent application Ser. No. 10/053,390, filed Jan. 16, 2002, thedisclosures of which are herein incorporated by reference.

Control subsystem 26 includes one or more instruments 48 that areoperable by a user to control the motion of blade 40. Instruments 48 mayinclude start/stop switches, speed controls, direction controls, etc.Control subsystem 26 also includes a logic controller 50 connected toreceive the user's inputs via instruments 48. Logic controller 50 isalso connected to receive a contact detection signal from detectionsubsystem 22. Further, the logic controller may be configured to receiveinputs from other sources (not shown) such as blade motion sensors,workpiece sensors, etc. In any event, the logic controller is configuredto control operative structure 12 in response to the user's inputsthrough instruments 48. However, upon receipt of a contact detectionsignal from detection subsystem 22, the logic controller overrides thecontrol inputs from the user and activates reaction subsystem 24 to stopthe motion of the blade. Various exemplary embodiments andimplementations of control subsystem 26 are described in more detail inU.S. Provisional Patent Application Ser. No. 60/225,059, filed Aug. 14,2000, U.S. patent application Ser. No. 09/929,237, filed Aug. 13, 2001,U.S. Provisional Patent Application Ser. No. 60/225,094, filed Aug. 14,2000 and U.S. patent application Ser. No. 09/929,234, filed Aug. 13,2001, the disclosures of which are herein incorporated by reference.

In the exemplary implementation shown in FIG. 2, brake mechanism 28includes a pawl 60 mounted adjacent the edge of blade 40 and selectivelymoveable to engage and grip the teeth of the blade. Pawl 60 may beconstructed of any suitable material adapted to engage and stop theblade. As one example, the pawl may be constructed of a relatively highstrength thermoplastic material such as polycarbonate, ultrahighmolecular weight polyethylene (UHMW), Acrylonitrile Butadiene Styrene(ABS), etc., or a metal such as aluminum, etc. It will be appreciatedthat the construction of pawl 60 will vary depending on theconfiguration of blade 40. In any event, the pawl is urged into theblade by a biasing mechanism such as a spring 66. In the illustrativeembodiment shown in FIG. 2, pawl 60 is pivoted into the teeth of blade40. It should be understood that sliding or rotary movement of pawl 60may also be used. The spring is adapted to urge pawl 60 into the teethof the blade with sufficient force to grip the blade and quickly bringit to a stop.

The pawl is held away from the edge of the blade by a restrainingmechanism such as a fusible member 70. The fusible member is constructedof a suitable material adapted to restrain the pawl against the bias ofspring 66, and also adapted to melt under a determined electricalcurrent density. Examples of suitable materials for fusible member 70include NiChrome wire, stainless steel wire, etc. The fusible member isconnected between the pawl and a contact mount 72. Preferably, fusiblemember 70 holds the pawl relatively close to the edge of the blade toreduce the distance pawl 60 must travel to engage blade 40. Positioningthe pawl relatively close to the edge of the blade reduces the timerequired for the pawl to engage and stop the blade. Typically, the pawlis held approximately 1/32-inch to ¼-inch from the edge of the blade byfusible member 70; however other pawl-to-blade spacings may also be usedwithin the scope of the invention.

Pawl 60 is released from its unactuated, or cocked, position to engageblade 40 by a release mechanism in the form of a firing subsystem 76.The firing subsystem is coupled to contact mount 72, and is configuredto melt fusible member 70 by passing a surge of electrical currentthrough the fusible member. Firing subsystem 76 is coupled to logiccontroller 50 and activated by a signal from the logic controller. Whenthe logic controller receives a contact detection signal from detectionsubsystem 22, the logic controller sends an activation signal to firingsubsystem 76, which melts fusible member 70, thereby releasing the pawlto stop the blade. Various exemplary embodiments and implementations ofreaction subsystem 24 are described in more detail in U.S. ProvisionalPatent Application Ser. No. 60/225,056, filed Aug. 14, 2000, U.S. patentapplication Ser. No. 09/929,240, filed Aug. 13, 2001, U.S. ProvisionalPatent Application Ser. No. 60/225,170, filed Aug. 14, 2000, U.S. patentapplication Ser. No. 09/929,227, filed Aug. 13, 2001, U.S. ProvisionalPatent Application Ser. No. 60/225,169, filed Aug. 14, 2000 and U.S.patent application Ser. No. 09/929,241, filed Aug. 13, 2001, thedisclosures of which are herein incorporated by reference.

It will be appreciated that activation of the brake mechanism mayrequire the replacement of one or more portions of safety system 18. Forexample, pawl 60 and fusible member 70 typically are single-usecomponents which must be replaced before the safety system is ready tobe used again. Thus, it may be desirable to incorporate one or moreportions of safety system 18 in a cartridge that can be easily replaced.For example, in the exemplary implementation depicted in FIG. 2, safetysystem 18 includes a replaceable cartridge 80 having a housing 82. Pawl60, spring 66, fusible member 70 and contact mount 72 are all mountedwithin housing 82. Alternatively, other portions of safety system 18 maybe mounted within the housing. In any event, after the reaction systemhas been activated, the safety system can be reset by replacingcartridge 80. The portions of safety system 18 not mounted within thecartridge may be replaced separately or reused as appropriate. Variousexemplary embodiments and implementations of a safety system using areplaceable cartridge are described in more detail in U.S. ProvisionalPatent Application Ser. No. 60/225,201, filed Aug. 14, 2000, U.S. patentapplication Ser. No. 09/929,236, filed Aug. 13, 2001, U.S. ProvisionalPatent Application Ser. No. 60/225,212, filed Aug. 14, 2000 and U.S.patent application Ser. No. 09/929,244, filed Aug. 13, 2001, thedisclosures of which are herein incorporated by reference.

In the exemplary embodiment illustrated in FIG. 2, reaction subsystem 24is configured to act on cutting tool 14 and stop rotation of blade 40.As mentioned above, reaction subsystem 24 may be configured also to acton a different portion of operative structure 12 to stop and/or reversethe translation of blade 40 toward the workpiece and the user's body.Otherwise, the blade may continue to move toward the user's body eventhough the blade has stopped rotating. For example, U.S. ProvisionalPatent Application Ser. No. 60/270,941, filed Feb. 22, 2001, U.S. patentapplication Ser. No. 10/052,273, filed Jan. 16, 2002, U.S. ProvisionalPatent Application Ser. No. 60/270,942, filed Feb. 22, 2001, U.S. patentapplication Ser. No. 10/052,806, filed Jan. 16, 2002, U.S. ProvisionalPatent Application Ser. No. 60/273,178, filed Mar. 2, 2001, U.S. patentapplication Ser. No. 10/052,274, filed Jan. 16, 2002, U.S. ProvisionalPatent Application Ser. No. 60/273,902, filed Mar. 6, 2001, U.S. patentapplication Ser. No. 10/050,085, filed Jan. 14, 2002, U.S. ProvisionalPatent Application Ser. No. 60/279,313, filed Mar. 27, 2001, and U.S.patent application Ser. No. 10/051,782, filed Jan. 15, 2002, thedisclosures of which are herein incorporated by reference, describevarious alternative embodiments of reaction subsystem 24 configured tostop any downward movement of the miter saw blade and/or move the bladeupward away from the workpiece and the user's body.

Turning attention now to FIGS. 3-5, another alternative embodiment isillustrated in which reaction subsystem 24 is configured to stop boththe rotation and downward movement of the blade. Exemplary miter saw 10includes a base assembly 90 having a base 92 adapted to support aworkpiece during cutting. Typically, one or more fences 94 are mountedon base 92 and adapted to prevent workpieces from shifting across thebase during cutting. Base 92 and fences 94 define a cutting zone 96 inwhich workpieces may be cut. Exemplary base assembly 90 also includes atilt mechanism 98 coupled to base 92.

As in the embodiments described above, blade 40 is mounted on arotatable arbor 42. The arbor is driven by a motor assembly (not shown)which is supported above base 92 by a pivot arm assembly 100. As shownin FIGS. 3 and 4, the pivot arm assembly is selectively pivotal towardand away from cutting zone 96 to cut workpieces with the blade. Inaddition, at least a portion of tilt mechanism 98 is selectivelytiltable relative to base 92 to make beveled cuts in the workpiece.

Pivot arm assembly 100 includes a housing 102 extending outward from oneend of an arm 104. The opposite end of arm 104 is connected to tiltmechanism 98 by a pivot coupling 106. Housing 102 is configured toextend at least partially around an upper portion of blade 40.Typically, pivot arm assembly 100 includes a spring or other biasingmechanism (not shown) adapted to maintain the housing and blade in afully upward position away from cutting zone 96 when the miter saw isnot in use.

Reaction subsystem 24 includes a brake mechanism 28 having at least onebrake pawl 60 engageable by an actuator 107. The actuator typicallyincludes a restraining mechanism adapted to hold the brake pawl awayfrom the blade against the urging of a biasing mechanism. In response toan activation signal, a release mechanism within the actuator releasesthe brake pawl from the restraining mechanism to pivot into the blade,usually stopping the blade within approximately 2-5 milliseconds.Optionally, brake pawl 60 and/or one or more components of actuator 106may be contained in a replaceable cartridge, such as indicated at 80 inFIG. 4. Exemplary actuators, restraining mechanisms, biasing mechanisms,release mechanisms, cartridges and brake pawls are described in moredetail above and in the incorporated references.

Brake pawl 60 is mounted on a movable pivot pin 108 configured to slidewithin a first set of channels 110 in either side of housing 102. Firstset of channels 110 define concentric arcs about arbor 42. As a result,pivot pin 108 is maintained at a constant radius from the arbor as itslides within the first set of channels. A positioning pin 112 extendsfrom one or both sides of actuator 106 to slide within a second set ofchannels 114. The second set of channels also define concentric arcsabout arbor 42 so that positioning pin 112 maintains a constant radiusfrom the arbor as it slides within the second set of channels. Sincebrake pawl 60 is coupled to actuator 112, both the brake pawl andactuator are maintained in a constant orientation relative to the arborand the perimeter of the blade as pivot pin 108 slides within first setof channels 110.

As shown in FIG. 5, brake pawl 60 is laterally positioned on pivot pin108 so that a central portion of the brake pawl is aligned with theblade. Brake mechanism 28 may include suitable positioning structure tomaintain the brake pawl aligned with the blade. For example, annularspacers may be placed on pivot pin 108 on either side of the brake pawlto butt against the inner sides of housing 102. Alternatively, the brakepawl may be constructed to have a width substantially equal to the innerwidth of the housing. In alternative embodiments where cartridge 80 isused, the cartridge may be sized to extend substantially from one innerside of the housing to the other. As a further alternative, the innersides of the housing may include projections which extend inward tocenter the cartridge or brake pawl relative to the blade.

Base assembly 90 also includes a brace member 116 extending upward fromtilt mechanism 98. In the exemplary embodiment, brace member 116 extendsupward from the tilt mechanism at an angle away from pivot arm assembly100 so that the pivot arm assembly is not obstructed from pivoting to afully raised position, as illustrated in FIG. 3. It will be appreciatedthat brace member 116 and tilt mechanism 98 may be formed as anintegral, unitary structure. Alternatively, the brace member and tiltmechanism may be formed separately and then coupled together. In anyevent, the brace member is coupled to the tilt mechanism so as toprevent any pivoting movement of the brace member toward or away fromthe cutting zone. However, the brace member is configured to tilt alongwith the tilt mechanism relative to the base when the miter saw isadjusted for bevel cuts.

Pivot pin 108 is coupled to brace member 116 by a linkage assembly 118.As best seen in FIG. 5, one end of linkage assembly 118 includes a forkstructure 120 pivotally coupled to a pivot pin 122 mounted in bracemember 116. The opposite end of linkage assembly 118 includes a forkstructure 124 pivotally coupled to each end of pivot pin 108. As shown,linkage assembly 118 is coupled to pivot pin 108 on either side of brakepawl 60. This provides increased stability and support when the brakepawl engages the blade. In an alternative embodiment, the linkageassembly may take the form of a pair of separate arms extending betweenpin 108 and pin 122 on either side of the brake pawl. As a furtheralternative, linkage assembly 118 may be configured to engage pivot pin108 and/or pivot pin 122 on only a single side of the brake pawl. Asanother alternative embodiment, the linkage assembly may be configuredto engage the center of pivot pin 108 (e.g., through a cut-out in thebrake pawl) and/or the center of pivot pin 122 (e.g., through a cut-outin brace member 116).

In any event, the linkage assembly pivots relative to brace member 116as the housing is pivoted toward and away from the cutting zone. Bracemember 116 pushes or pulls pivot pin 108 and brake pawl 60 around theperimeter of the blade in first set of channels 110 as the housing israised or lowered. Thus, the brake pawl is maintained at a constantdistance from the brace member regardless of the position of thehousing.

In response to an activation signal from a control subsystem (notshown), brake pawl 60 is pivoted into the teeth of blade 40. When thebrake pawl engages the blade the angular momentum of the blade producesa force on the brake pawl that tends to urge the brake pawl to move in aclockwise direction along first set of channels 110. In other words, atleast a portion of the angular momentum of the blade is transferred tothe brake pawl. The force on brake pawl 60 is transferred to bracemember 116 by linkage assembly 118. Linkage assembly 118 may beconstructed of any relatively rigid material adapted to support brakepawl 60 during braking of the blade, including metal, plastic, etc.

Brace member 116 prevents the brake pawl from sliding clockwise withinfirst set of channels 110 unless housing 102 pivots upward away from thecutting zone. As a result, pivot arm assembly 100 will be urged upwardby engagement of the brake pawl with the blade. The amount of upwardforce on the blade will depend, at least partially, on the length ofbrace member 116. As the length of the brace member is increased, theupward force on the blade during braking will likewise increase.Typically, the length of the brace member is selected so that the upwardforce on the blade during braking is sufficient to stop any downwardmotion of the housing under normal operating conditions (i.e., thehousing is pivoted downward toward the cutting zone at a normal speed).Optionally, the length of the brace member is selected so that theupward force on the blade during braking is sufficient to overcome andreverse any normal downward momentum of the housing and blade, therebyretracting the blade upward away from cutting zone 96.

In any event, brake pawl 60 is arranged and supported to convert atleast a portion of the kinetic energy of the rotating blade into anupward force on the blade and housing. Thus, exemplary brake mechanism28 is configured to stop both the rotation of the blade and any downwardmovement of the blade using a single brake pawl. As a result, only asingle cartridge or brake pawl need be replaced after the brakemechanism has been triggered.

Since the upward force on the blade and housing is produced by the rapiddeceleration of the blade by the brake pawl, the upward force is onlytemporary. Once the rotation of the blade has stopped, the housing isfree to pivot toward or away from the cutting zone. Nevertheless, theblade will remain locked against further rotation until the cartridge isremoved.

Housing 102 may include one or more sections 126 which may be removed orrepositioned to allow installation and removal of the cartridge or brakepawl and actuator. Pivot pin 108 is typically removed by sliding itcompletely through the brake pawl. Positioning pin 112 may also be slidcompletely through the actuator and/or cartridge. Alternatively,positioning pin 112 may be dual spring-loaded pins which can bedepressed to allow the cartridge to be installed and removed moreeasily. Optionally, housing 102 may include one or more removable coversadapted to cover one or both of the first and second set of channelsduring normal operation. It will be appreciated that housing 102 and thecomponents of the brake mechanism may be configured in any of a varietyof different ways to allow the brake mechanism to be easily replaced.

While one particular embodiment has been described above, manymodifications and alterations are possible. For example, FIGS. 6-9illustrate an alternative exemplary embodiment in which the brakemechanism includes a brake pawl support structure that pivots within thehousing. As shown, the brake mechanism includes one or more radialsupport arms 128 adapted to support cartridge 80 at a constant radialdistance and orientation about arbor 42. Support arms 128 are configuredto pivot about the elongate central axis of arbor 42. Each arm includesan annular collar portion 130 configured to fit on and swing about oneof a pair of support rings 132. One support ring 132 extends from theinner surface of housing 102, while the other support ring extends frommotor assembly 16. Collar portions 130 may be retained on support rings132 by ring clips 134 or any other suitable mechanism. It will beappreciated that support arms 128 may alternatively be coupled to pivotabout the arbor in a variety of other ways such as are known to those ofskill in the art.

Cartridge 80 is coupled to support arms 128 by a pivot pin 136 and apositioning pin 138. The pivot and positioning pins maintain thecartridge at a constant radial distance and orientation relative to theperimeter of the blade as support arms 128 pivot around the arbor. Thesupport arms are coupled to a brace member 116 by one or more linkages140. The rear end of each linkage 140 is pivotally coupled to bracemember 116 by a pivot pin 142. The front end of each linkage ispivotally coupled to a different one of support arms 128 by one or morepivot pins 144. In the exemplary embodiment, pivot pins 144 are mountedin outwardly projecting shoulder regions 146 formed in each support arm128. Shoulder regions 146 are configured to ensure pivot pins 144 andthe front ends of linkages 140 remain above arbor 42 at all operablepositions of pivot arm assembly 100.

In the exemplary embodiment, linkages 140 extend forward from bracemember 116 through one or more holes 148 in the rear of housing 102.Therefore, housing 102 requires no arcuate channels for receiving pins136, 138 or 144. Furthermore, linkages 140 should not interfere withstandard blade guards (not shown) that typically cover the perimeter ofthe housing and blade. Indeed, a front section of housing 102 mayoptionally be constructed to telescope around the exterior of theremainder of the housing to allow a user to have greater access to theblade. Alternatively, linkages 140 may be disposed on the exterior ofthe housing, in which case pivot pin 136 and positioning pin 138 wouldextend through arcuate channels or similar openings in the housing.Although linkages 140 are depicted as separate structural elements, itwill be appreciated that the linkages may be formed as an unitary memberwith spaced-apart arms, etc.

Comparing FIGS. 6 and 7, it can be seen that as pivot arm assembly 100pivots about pivot coupling 106, linkages 140 cause support arms 128 topivot about arbor 42 in the opposite direction. Thus, cartridge 80 andbrake pawl 60 are counter-pivotally coupled to the pivot arm assembly.As the pivot arm assembly and blade pivot in a clockwise direction (asseen in FIGS. 6 and 7) downward toward cutting zone 96, the cartridgeand brake pawl pivot in a counter-clockwise direction about the arbor.Conversely, as the pivot arm assembly and blade pivot in acounter-clockwise direction (as seen in FIGS. 6 and 7) upward away fromcutting zone 96, the cartridge and brake pawl pivot in a clockwisedirection about the arbor.

The brake pawl (not shown) is mounted on pivot pin 136 to pivot into theteeth of blade 40 upon receipt of an activation signal by the cartridge.When the brake pawl engages the rotating blade, the angular momentum ofthe blade tends to force the brake pawl to move upward and forward in aclockwise direction (as seen in FIG. 6) about the arbor. Consequently,radial support arms 128 are urged to pivot in a clockwise direction (asseen in FIG. 6) about the arbor. Since the radial support arms areconnected to brace member 116 by linkages 140, any clockwise force onthe radial support arms is translated into a counter-clockwise forceabout pivot coupling 106 on housing 102. In other words, when the brakepawl engages the blade, the housing and blade are urged upward away fromcutting zone 96.

It will be appreciated that the amount of upward force on the housingwill depend on the specific arrangement of brace member 116, linkages140 and radial support arms 128. The counter-clockwise force on supportarms 128 due to any downward momentum and/or force on the pivot armassembly will have a lesser moment than the clockwise force due to thebrake pawl engaging the blade. This is because linkages 140 are coupledto the support arms at a radial position closer to the pivot point ofthe support arms than is the brake pawl. The ratio of the clockwiseforce-moment to the counter-clockwise force-moment will depend on theratio of the distances between pivot pin 136 and arbor 42, and betweenpivot pins 144 and arbor 42. Additionally, the height of pivot pin 142above pivot coupling 106, relative to the height of pivot pins 144 abovearbor 42 will also effect the ratio of the upward force on the pivot armassembly due to the brake pawl to any downward momentum and/or force onthe pivot arm assembly.

Typically, the height of pivot pin 142 above pivot coupling 106, and theposition of pivot pins 144 on support arms 128 are selected to ensurethat, under normal operating conditions, any downward movement of theblade toward the cutting zone is stopped when the brake pawl engages theblade. Optionally, the height of pivot pin 142 above pivot coupling 106,and the position of pivot pins 144 on support arms 128 may be selectedto ensure that the clockwise force-moment on the support arms is greaterthan the normal counter-clockwise force-moment when the brake pawlengages the blade. In such case, the blade is pushed or retracted upwardand at least partially away from the cutting zone when a dangerouscondition is detected such as contact between the user's body and theblade.

Once the brake pawl has engaged and stopped the blade, pivot armassembly 100 is free to pivot about pivot coupling 106. Housing 102 mayinclude a removable portion through which the cartridge can be replaced.Alternatively, the radial support arms may be uncoupled from bracemember 116, as shown in FIG. 9. In the exemplary embodiment, the supportarms are uncoupled from the brace member by disconnecting linkages 140from pivot pin 142. Since the brake pawl usually is wedged onto theblade after being triggered, blade 40 may be rotated until the cartridgeis exposed below the housing. Pivot pin 136 and positioning pin 138 maythen be removed. Alternatively, positioning pin 138 may be dualspring-loaded pins which can be depressed to disengage the radialsupport arms. As further alternative, the interior surfaces of radialsupport arms 128 may include recessed channels 154 adapted to allowpivot pin 136 to slide into place. Position pin(s) 138 may then beinstalled to hold the cartridge in the operable position relative to theblade. After the used cartridge is replaced with a new cartridge, thecartridge and support arms are pivoted up into the housing and thelinkages are reconnected to pivot pin 142. When removing or installingthe blade, arbor nut 150 may be accessed through an opening 152 in thehousing.

As described above, the present invention provides a miter saw which issubstantially safer than existing saws. The miter saw includes a safetysystem 18 adapted to detect the occurrence of a dangerous condition andstop movement of the blade and/or the pivot arm to prevent seriousinjury to a user. The safety system may be adapted for use on a varietyof saws in addition to miter saws. Several examples of modifications andvariations, as well as further detailed descriptions of miter saws andother saws may be found in the following references, the disclosures ofwhich are herein incorporated by reference: PCT Patent ApplicationSerial No. PCT/US00/26812, filed Sep. 29, 2000; U.S. patent applicationSer. No. 09/676,190, filed Sep. 29, 2000; U.S. Provisional PatentApplication Ser. No. 60/275,595, filed Mar. 13, 2001; U.S. ProvisionalPatent Application Ser. No. 60/273,177, filed Mar. 2, 2001; U.S. patentapplication Ser. No. 10/052,705, filed Jan. 16, 2002; U.S. ProvisionalPatent Application Ser. No. 60/233,459, filed Sep. 18, 2000; U.S.Provisional Patent Application Ser. No. 60/225,210, filed Aug. 14, 2000;U.S. patent application Ser. No. 09/929,425, filed Aug. 13, 2001; U.S.Provisional Patent Application Ser. No. 60/225,058, filed Aug. 14, 2000;U.S. patent application Ser. No. 09/929,235, filed Aug. 13, 2001; U.S.Provisional Patent Application Ser. No. 60/225,057, filed Aug. 14, 2000;U.S. patent application Ser. No. 09/929,238, filed Aug. 13, 2001; U.S.Provisional Patent Application Ser. No. 60/157,340, filed Oct. 1, 1999;U.S. Provisional Patent Application Ser. No. 60/279,313, filed Mar. 27,2001; U.S. patent application Ser. No. 10/051,782, filed Jan. 15, 2002;U.S. Provisional Patent Application Ser. No. 60/292,081, filed May 17,2001; U.S. patent application Ser. No. 09/955,418, filed Sep. 17, 2001;U.S. Provisional Patent Application Ser. No. 60/298,207, filed Jun. 13,2001; U.S. patent application Ser. No. 10/172,553, filed Jun. 13, 2002;U.S. Provisional Patent Application Ser. No. 60/302,937, filed Jul. 2,2001; U.S. patent application Ser. No. 10/189,031, filed Jul. 2, 2002;U.S. Provisional Patent Application Ser. No. 60/302,916, filed Jul. 3,2001; U.S. patent application Ser. No. 10/189,027, filed Jul. 2, 2002;U.S. Provisional Patent Application Ser. No. 60/307,756, filed Jul. 25,2001; U.S. patent application Ser. No. 10/202,928, filed Jul. 25, 2002;U.S. Provisional Patent Application Ser. No. 60/324,729, filed Sep. 24,2001; U.S. Provisional Patent Application Ser. No. 60/335,970, filedNov. 13, 2001; and U.S. Provisional Patent Application Ser. No.60/351,797, filed Jan. 25, 2002.

It is believed that the disclosure set forth above encompasses multipledistinct inventions with independent utility. While each of theseinventions has been disclosed in its preferred form, the specificembodiments thereof as disclosed and illustrated herein are not to beconsidered in a limiting sense as numerous variations are possible. Thesubject matter of the inventions includes all novel and non-obviouscombinations and subcombinations of the various elements, features,functions and/or properties disclosed herein. No single feature,function, element or property of the disclosed embodiments is essentialto all of the disclosed inventions.

1. A miter saw comprising: a base adapted to support a workpiece duringcutting; a motor; a rotatable, circular blade driven by the motor, wherethe blade includes teeth around its periphery; a pivot arm assemblyassociated with the base and supporting the blade, where the pivot armassembly is adapted to pivot toward and away from the base to move theblade toward and away from the base; and a safety system having adetection subsystem adapted to detect the occurrence of an unsafecondition between a person and the blade, and a reaction subsystemadapted to mitigate the unsafe condition, where the reaction subsystemincludes a brake mechanism adjacent the blade, and where at least a partof the brake mechanism is adapted to pivot into the teeth of the bladeto engage the blade.
 2. The miter saw of claim 1, where the unsafecondition is contact between a person and the blade.
 3. The miter saw ofclaim 1, where the unsafe condition is proximity between a person andthe blade.
 4. The miter saw of claim 1, where the brake mechanismincludes a brake pawl and where the brake pawl is adapted to pivot intothe teeth of the blade.
 5. The miter saw of claim 4, where the blade issubstantially planar, and where the brake pawl is adapted to pivotaround an axis generally perpendicular to the plane of the blade.
 6. Themiter saw of claim 1, where the blade is substantially planar and whereat least a part of the brake mechanism is adapted to pivot into theteeth of the blade around an axis generally perpendicular to the planeof the blade.
 7. The miter saw of claim 1, further comprising a pivotpin supporting a part of the brake mechanism adapted to pivot into theteeth of the blade.
 8. The miter saw of claim 1, further comprising asupport arm holding at least a portion of the brake mechanism adjacentthe teeth of the blade.
 9. The miter saw of claim 1, where the brakemechanism includes a brake pawl adapted to pivot into the teeth of theblade, and further comprising at least one support arm holding the brakepawl adjacent the teeth of the blade.
 10. The miter saw of claim 9,where the blade is substantially planar, and where the brake pawl isadapted to pivot around an axis generally perpendicular to the plane ofthe blade.
 11. The miter saw of claim 10, further comprising a pivot pinpositioned generally perpendicularly relative to the plane of the bladeand supported at least partially by at least one support arm, and wherethe brake pawl is adapted to pivot on the pivot pin.
 12. A miter sawcomprising: a base adapted to support a workpiece during cutting; amotor; a rotatable, circular, generally planar blade driven by themotor, where the blade includes teeth around its periphery; a pivot armassembly associated with the base and supporting the blade, where thepivot arm assembly is adapted to pivot toward and away from the base tomove the blade toward and away from the base; and a safety system havinga detection subsystem adapted to detect the occurrence of an unsafecondition between a person and the blade, and a reaction subsystemadapted to mitigate the unsafe condition, where the reaction subsystemincludes a brake configured to pivot into the teeth of the blade aroundan axis generally perpendicular to the plane of the blade.
 13. The mitersaw of claim 12, where the unsafe condition is contact between a personand the blade.
 14. The miter saw of claim 12, where the unsafe conditionis proximity between a person and the blade.
 15. The miter saw of claim12, further comprising a pivot pin supporting the brake.
 16. The mitersaw of claim 12, further comprising at least one support arm holding thebrake adjacent the teeth of the blade.
 17. The miter saw of claim 16,further comprising a pivot pin positioned generally perpendicularlyrelative to the plane of the blade and supported at least partially byat least one support arm.
 18. The miter saw of claim 17, where the brakeis adapted to pivot on the pivot pin.
 19. A miter saw comprising: a baseadapted to support a workpiece during cutting; a fence on the base; amotor; a rotatable, circular blade driven by the motor, where the bladeincludes teeth around its periphery; a pivot arm assembly associatedwith the base and supporting the blade, where the pivot arm assembly isadapted to pivot toward and away from the base to move the blade towardand away from the base; and a safety system having a detection subsystemadapted to detect the occurrence of an unsafe condition between a personand the blade, and a reaction subsystem adapted to mitigate the unsafecondition, where the reaction subsystem includes brake means forpivoting into the teeth of the blade to stop the rotation of the bladeif an unsafe condition is detected by the detection subsystem.
 20. Themiter saw of claim 19 where the brake means is supported by support armmeans for holding the brake means adjacent the teeth of the blade.